Hilde Møller Knag is Albert Knag's daughter. She is the reason that Sophie and Alberto were created in the first place. Hilde bears a strong resemblance to Sophie in that she learns to think philosophically alongside Sophie. She is compassionate, because she feels for Alberto and Sophie, even though they appear to be fictional characters. Hilde believes that Sophie exists somewhere, although she cannot explain how. At age fifteen, she still retains enough belief in the mysterious nature of life and the inexplicable mysteries that surround us to hold a firm belief in something that would be characterized as impossible. But it turns out that, although she does not know it, Hilde is correct—Sophie and Alberto do "exist" in some strange way. Hilde represents that sort of person who can think and reason well but also is willing to believe in what she feels to be true regardless of what anyone else thinks. So, in some ways, Hilde represents that ideal reader for Gaarder's book. Sophie's World is designed to be both a novel and a history of philosophy, and someone like Hilde would understand and think about the philosophical ideas that are put forth but would also be partial to the fantastical aspects of the story.